netdev - [PATCH v4 bpf-next 6/9] libbpf: add raw tracepoint attach API

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Message-ID: <20190629034906.1209916-7-andriin@fb.com>
Date:   Fri, 28 Jun 2019 20:49:03 -0700
From:   Andrii Nakryiko <andriin@...com>
To:     <andrii.nakryiko@...il.com>, <bpf@...r.kernel.org>,
        <netdev@...r.kernel.org>, <ast@...com>, <daniel@...earbox.net>,
        <kernel-team@...com>, <sdf@...ichev.me>, <songliubraving@...com>
CC:     Andrii Nakryiko <andriin@...com>
Subject: [PATCH v4 bpf-next 6/9] libbpf: add raw tracepoint attach API

Add a wrapper utilizing bpf_link "infrastructure" to allow attaching BPF
programs to raw tracepoints.

Signed-off-by: Andrii Nakryiko <andriin@...com>
Acked-by: Song Liu <songliubraving@...com>
---
 tools/lib/bpf/libbpf.c   | 37 +++++++++++++++++++++++++++++++++++++
 tools/lib/bpf/libbpf.h   |  3 +++
 tools/lib/bpf/libbpf.map |  1 +
 3 files changed, 41 insertions(+)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 8ad4f915df38..f8c7a7ecb35e 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -4263,6 +4263,43 @@ struct bpf_link *bpf_program__attach_tracepoint(struct bpf_program *prog,
 	return link;
 }
 
+static int bpf_link__destroy_fd(struct bpf_link *link)
+{
+	struct bpf_link_fd *l = (void *)link;
+
+	return close(l->fd);
+}
+
+struct bpf_link *bpf_program__attach_raw_tracepoint(struct bpf_program *prog,
+						    const char *tp_name)
+{
+	char errmsg[STRERR_BUFSIZE];
+	struct bpf_link_fd *link;
+	int prog_fd, pfd;
+
+	prog_fd = bpf_program__fd(prog);
+	if (prog_fd < 0) {
+		pr_warning("program '%s': can't attach before loaded\n",
+			   bpf_program__title(prog, false));
+		return ERR_PTR(-EINVAL);
+	}
+
+	link = malloc(sizeof(*link));
+	link->link.destroy = &bpf_link__destroy_fd;
+
+	pfd = bpf_raw_tracepoint_open(tp_name, prog_fd);
+	if (pfd < 0) {
+		pfd = -errno;
+		free(link);
+		pr_warning("program '%s': failed to attach to raw tracepoint '%s': %s\n",
+			   bpf_program__title(prog, false), tp_name,
+			   libbpf_strerror_r(pfd, errmsg, sizeof(errmsg)));
+		return ERR_PTR(pfd);
+	}
+	link->fd = pfd;
+	return (struct bpf_link *)link;
+}
+
 enum bpf_perf_event_ret
 bpf_perf_event_read_simple(void *mmap_mem, size_t mmap_size, size_t page_size,
 			   void **copy_mem, size_t *copy_size,
diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index 60611f4b4e1d..f55933784f95 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -182,6 +182,9 @@ LIBBPF_API struct bpf_link *
 bpf_program__attach_tracepoint(struct bpf_program *prog,
 			       const char *tp_category,
 			       const char *tp_name);
+LIBBPF_API struct bpf_link *
+bpf_program__attach_raw_tracepoint(struct bpf_program *prog,
+				   const char *tp_name);
 
 struct bpf_insn;
 
diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
index 3c618b75ef65..e6b7d4edbc93 100644
--- a/tools/lib/bpf/libbpf.map
+++ b/tools/lib/bpf/libbpf.map
@@ -171,6 +171,7 @@ LIBBPF_0.0.4 {
 		bpf_object__load_xattr;
 		bpf_program__attach_kprobe;
 		bpf_program__attach_perf_event;
+		bpf_program__attach_raw_tracepoint;
 		bpf_program__attach_tracepoint;
 		bpf_program__attach_uprobe;
 		btf_dump__dump_type;
-- 
2.17.1